This application claims the priority of Korean Patent Application No. 2002-40846, filed on Jul. 12, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to the field of a semiconductor package assembly, and more particularly, to a dicing tape attaching unit, and to an in-line system including the dicing tape attaching unit.
2. Description of the Related Art
Numerous semiconductor chips can be formed from a semiconductor wafer manufactured in a wafer manufacturing process. When a wafer is diced, the semiconductor chips are created. However, these individual semiconductor chips are incomplete and not able to function unless they have external connection terminals, such as solder balls or leads. These external connection terminals can be easily damaged by shock or impact. A semiconductor package assembling process is employed to seal a semiconductor chip to protect it from external shock and impact, and to permit an effective external connection terminal to be formed.
In the general order in which a semiconductor package is assembled, a wafer is attached to a dicing tape using a ring frame. Then, a dicing process is performed in which individual chips are separated from the wafer using a dicing blade formed of diamond. Subsequently, the individual chips are adhered onto a lead frame or substrate, and a wire bonding process is then performed.
In order to reduce the size of semiconductor packages, a process of grinding down the back-side of a wafer to reduce its thickness is often performed before attaching the wafer to a dicing tape. Such a wafer back-side grinding process is mainly performed in improved semiconductor package assembling processes, such as multi chip package (MCP) processes, double die package (DDP) processes, thin profile small out-line package (TSOP) processes, and ultra thin profile small out-line package (USOP) processes.
In general, the thickness of a wafer after undergoing a wafer back-side grinding process is reduced to about 100–200 μm. The wafer after grinding is easily damaged by external shock, and sometimes tends to warp. Thus, there is often difficulty when the wafer is transferred to an assembling unit of a semiconductor package process, or when the wafer is handled in the assembling unit. In order to overcome such difficulty, an in-line system in which a wafer grinder and a unit for attaching a dicing tape to a wafer are formed as a single entity have been developed.
FIG. 1 is a block diagram illustrating a conventional in-line system in which a wafer grinder and a dicing tape attaching unit are formed as a single entity. Referring to FIG. 1, a conventional in-line system 10 for performing a semiconductor package assembling process. System 10 includes a wafer loading unit 12 which loads a wafer to which a lamination tape is attached thereinto so as to prevent contamination of the top side of the wafer. System 10 also includes a wafer grinder 14 which grinds the back side of the loaded wafer to reduce the thickness of the wafer, a UV light radiating unit 16 which irradiates UV light onto the top side of the wafer, a dicing tape attaching unit 18 which attaches a dicing tape to the back side of the wafer using a ring frame, a lamination tape detaching unit 20 which detaches the lamination tape from the top side of the wafer, and a wafer unloading unit 22 which unloads the wafer from system 10.
The purpose of irradiating the wafer with UV light is to reduce an adhesive force between the lamination tape and the top side of the wafer. Accordingly, after irradiating the wafer with UV light, the lamination tape can be effectively removed from the top side of the wafer. Here, the dicing tape attaching unit 18 attaches only a general dicing tape to the back side of the wafer.
FIG. 2 is a cross-sectional view of a general dicing tape 30 used in a semiconductor package assembling process. Specifically, the general dicing tape 30 includes a base film 32, formed of polyethylene (PE) and an adhesive layer 34, which is formed of an acrylic polymeric material and is disposed on the base film 32. The adhesive layer 34 has an adhesive property that is reduced by UV light. The general dicing tape 30 further includes a liner film 36 located on the adhesive layer 34. The liner film 36 protects the adhesive layer 34 and is formed of polyethylene terephthalate (PET). Thus, when the general dicing tape 30 is attached to the back side of the wafer using a ring frame, the adhesive layer 34 including the base film 32 is attached to the back side of the wafer and the ring frame, and the liner film 36 is peeled off from the adhesive layer of the general dicing tape 30.
In a subsequent die bonding process, a semiconductor chip having a thickness of less than 100 μm is attached to a chip paddle of a lead frame or substrate, using liquid epoxy. In the case of using liquid epoxy, the semiconductor chip is very thin, and exhibits a die tilt defect. The die tilt defect occurs when a semiconductor chip is not attached in a level state and but is instead in a tilted state. In order to solve this problem, technology for adhering a semiconductor chip to a chip paddle of a lead frame or substrate using an adhesive tape, not a liquid epoxy, has been developed. In this case, a dicing tape including an adhesive tape, i.e., a tape that has been previously cut to a predetermined size, which is referred to as a pre-cut dicing tape. The pre-cut dicing tape is used in a die bonding process. However, the pre-cut dicing tape is applied in a dicing tape attaching process performed as part of the semiconductor package assembling process.
Referring to FIGS. 3 and 4, A refers to a circular pre-cut line and B refers to a pre-cut portion inside the circular pre-cut line A. The circular pre-cut portion B is attached to a wafer and a ring frame (not shown). A portion outside of A is wound together with a liner film 48. FIG. 4 shows a cross-sectional view of the pre-cut dicing tape 40. In particular, a base film 42a and 42b is formed of polyethylene (PE) and is located on the lowermost portion of the pre-cut dicing tape 40. An inner portion of the base film 42, i.e., the pre-cut portion B, marked 42a, and an outer portion of the base film 42, marked 42b, are separated by the pre-cut line A. Also, an expanding film 44a, 44b and an adhesive film 46 are formed on the respective base film 42a, 42b. 
The expanding film 44a, 44b attaches the ring frame to the base film 42a. The adhesive film 46 serves to attach a semiconductor chip to a die pad of a lead frame or substrate, instead of liquid epoxy used in the die bonding process. Last, the liner film 48 is formed of polyethylene terephthalate (PET) and protects the expanding film 44a, 44b and the adhesive film 46. After the pre-cut portion B is adhered to the ring frame or wafer, the other portion of the pre-cut line A is withdrawn together with the base film 42b and the expanding film 44b outside the pre-cut portion B.
However, the in-line system 10 of FIG. 1 does not attach the pre-cut dicing tape shown in FIGS. 3 and 4 to the wafer. Also, a dicing tape attaching unit that can attach only a pre-cut dicing tape to a wafer does not perform a wafer back side grinding function, and is used only in an independent process of only attaching the dicing tape to the wafer. Thus, in order to use a pre-cut dicing tape, not an in-line system but a dicing tape attaching unit that attaches only a pre-cut dicing tape to a wafer should be purchased. This causes the following disadvantages.
First, more assembling units are required, so manufacturing costs increase. Second, more assembling units are required, so the space occupied by a semiconductor package assembling line increases. Third, when a wafer made thin by performing a wafer back side grinding process is transferred by an assembling unit, warping of the wafer occurs and there is danger of fracturing the thin wafer.